Method and Apparatus for Uploading Radio Maps

ABSTRACT

In accordance with an example embodiment of the present invention, an apparatus comprises a first receiver configured to receive a first partial radio map and a second partial radio map, a processor configured to compare the first partial radio map and the second partial radio map, and the processor further configured to determine to replace the first partial radio map with the second partial radio map based at least in part on a result of the comparison.

TECHNICAL FIELD

The present application relates generally to updating radio maps.

BACKGROUND

Modern global cellular and non-cellular positioning technologies arebased on generating large global databases containing information oncellular and non-cellular signals. The information may originateentirely or partially from users of these positioning technologies. Thisapproach may also be referred to as “crowd-sourcing”.

Information provided by users may be in the form of “fingerprints”,which contain a location that is estimated based on, for example,received satellite signals of a global navigation satellite system,GNSS, and measurements taken from one or more radio interfaces forsignals of a cellular and/or non-cellular terrestrial system. A locationmay comprise an area surrounding a geographical position, for example.In the case of measurements on cellular signals, the results of themeasurements may contain a global and/or local identification of thecellular network cells observed, their signal strengths and/or pathlosses and/or timing measurements like timing advance, TA, or round-triptime. For measurements on wireless local area network, WLAN, signals, asan example of signals of a non-cellular system, the results of themeasurements may contain at least one of a basic service setidentification, BSSID, like the medium access control, MAC, address ofobserved access points, APs, the service set identifier, SSID, of theaccess points, and the signal strengths of received signals. A receivedsignal strength indication, RSSI, or physical reception level may beexpressed in dBm units with a reference value of 1 mW, for example.

Such data may then be transferred to a server or cloud, where the datamay be collected and where further models may be generated based on thedata for positioning purposes. Such further models can be coverage areaestimates, communication node positions and/or radio channel models,with base stations of cellular communication networks and access pointsof WLANs being exemplary communication nodes. In the end, these refinedmodels, also known as radio maps, RM, may be used for estimating theposition of mobile terminals.

Fingerprints do not necessarily have to comprise a GNSS based position.They may also include cellular and/or WLAN measurements only. In thiscase the fingerprint could be assigned a position for example based on aWLAN based positioning in a server. Such self-positioned fingerprintscan be used to learn cellular network information, in case there arecellular measurements in the fingerprint. Moreover, in a set of WLANmeasurements in a fingerprint there may be, in addition to measurementsfor known WLAN access points, also measurements for unknown accesspoints and the position of the unknown access points can be learnedthrough these self-positioned fingerprints. Finally, more data can belearnt of previously known access points based on self-positionedfingerprints.

It may be noted that even when using a mobile terminal havingGNSS-capabilities, a user may benefit from using cellular/non-cellularpositioning technologies in terms of time-to-first-fix and powerconsumption. Also, not all applications require a GNSS-based position.Furthermore, cellular/non-cellular positioning technologies work indoorsas well, which is generally a challenging environment for GNSS-basedtechnologies.

SUMMARY

Various aspects of examples of the invention are set out in the claims.

According to a first aspect of the present invention, an apparatuscomprises a first receiver configured to receive a first partial radiomap and a second partial radio map, a processor configured to comparethe first partial radio map and the second partial radio map, and theprocessor further configured to determine to replace the first partialradio map with the second partial radio map based at least in part on aresult of the comparison.

According to a second aspect of the present invention, a methodcomprises comparing a first partial radio map and a second partial radiomap, and determining to replace the first partial radio map with thesecond partial radio map based at least in part on a result of thecomparison.

According to further aspects of the present invention, computer programsare provided that are configured to cause methods in accordance with thesecond aspect to be performed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of example embodiments of the presentinvention, reference is now made to the following descriptions taken inconnection with the accompanying drawings in which:

FIG. 1 shows an example architecture of a positioning system;

FIG. 2 shows an example system for generating and distributing partialRMs for offline usage in user terminals;

FIG. 3 shows an apparatus embodying a process for updating radio mapsaccording to an example embodiment of the invention;

FIG. 4 is a flow diagram showing operations for updating radio maps inaccordance with at least one embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Positioning systems may function in two modes. The first mode is aterminal-assisted mode, in which a terminal performs measurements ofcellular and/or non-cellular air interface signals and provides resultsof the measurements to a positioning server hosting a global cellularand/or non-cellular RM database. The server then provides a positionestimate back to the terminal. This methodology is called onlinepositioning and requires the terminal to have data connectivity wheneverpositioning service is needed.

The second mode is a terminal-based mode, an offline positioningtechnique, in which a terminal has a local copy of a RM, called apartial RM. This partial RM is a subset of the global RM in form of WLANRM offline files, for example. These files may be in the form of adatabase or any other form that is readable by a computer. There may bemultiple such files, since it may be advantageous not to have a singleglobal file, but several smaller ones so that the terminal may onlydownload partial RM for a specific area, for example, a country or acity where a need for positioning is anticipated. This subset can alsobe pre-installed on the terminal. Offline positioning techniques do notrequire the terminal to have data connectivity whenever positioningservice is needed.

Offline positioning may be advantageous from a service perspectivebecause it helps reduce load on positioning servers. Also, since theterminals are capable of positioning themselves without contacting apositioning server, the terminals may remain location aware all thetime. Additionally, time-to-first-fix may be very short, since thedevice does not need to contact the server.

WLAN RM offline files can be very large in size. As an example, in anurban/suburban area covering roughly 10×10 km, there can be more than 10million APs. This results in an average density of one AP every 10 m² or400,000 APs per 2×2 km tile. Transferring location information for eachof these APs from a server to a terminal consumes a lot of serverresources, network bandwidth, storage space in the terminal and it canalso be quite expensive to the consumer in the form of data charges.Hence, it may be preferable to have small WLAN RM offline files. Inaddition, a WLAN AP environment may be highly dynamic and new APs mayappear, existing APs may become obsolete and AP locations may change,for example. Resultantly, radio maps installed on a device may need tobe refreshed, possibly more than once.

To reduce size of a radio map and corresponding WLAN RM offline files,those APs which do not significantly affect accuracy and availability ofa radio map may be excluded from the radio map. Availability of apositioning system is defined as the ratio of the number of successfulpositioning events to the total number of positioning requests. It canbe appreciated that both accuracy and availability are important metricsaffecting user experience. A further reduction in size of a partialradio map file can be achieved by compressing identifiers of APcomprised in the partial radio map into a smaller number of bits byutilizing a digital compression algorithm. But even after excluding APsfrom a partial radio map and utilizing compressed AP identifiers, sizesof partial radio map files may still be prohibitively big for frequentdownloads by user terminals. Thus, it may be desirable to avoiddownloading a newer version of a partial radio map to a user terminal,unless it's necessary for maintaining an acceptable level of accuracyand availability in offline positioning.

Embodiments of the present invention relate to comparing a new and aprevious version of a partial radio map and determining based upon thecomparison, if a new radio map should be published for positioningclients, such as user terminals, to download. Based upon the comparison,only if significant changes have taken place in a radio map environment,the new version of the partial radio map is published on a downloadserver for positioning clients to download. Otherwise, positioningclients are allowed to use an older version if the reduction inperformance of the older radio map compared to its newer version isexpected to be insignificant.

FIG. 1 shows an example architecture of a positioning system. Thepositioning system of FIG. 1 comprises a GNSS 101, a user terminal 102,a cellular network 103, WLAN systems 104, a positioning server 105, acollection/learning server 106 and a global RM database 107. Positioningserver 105 and collection/learning server 106 may be co-located in asingle site or apparatus, or alternatively they may be distinct in thesense that positioning server 105 is external to collection/learningserver 106 and collection/learning server 106 is external to positioningserver 105. Global RM database may be a standalone node, or it may becomprised in collection/learning server 106 and/or positioning server105. The user terminal 102 may receive its GNSS based position from theGNSS 101. The GNSS 101 could be GPS, GLONASS or any other satellitebased navigation system. The user terminal may also receive radiosignals from the cellular network 103. The cellular network 103 could bebased on any kind of cellular system, for instance a GSM system, a 3rdGeneration Partnership Project, 3GPP, based cellular system like a WCDMAsystem or a time division synchronous CDMA, TD-SCDMA, system, forexample supporting high speed packet access, HSPA, a 3GPP2 system like aCDMA2000 system, a long term evolution, LTE, or LTE-Advanced system, orany other type of cellular system, like a WiMAX system. Cellular network103 comprises a plurality of base stations or base transceiver stationsas communication nodes. Furthermore, user terminal 102 may also receivesignals from WLANs 104. WLANs 104 comprise at least one access point asa communication node. WLANs 104 may be based upon the IEEE 802.11standards, for example.

The user terminal 102 comprises a processor 1021, and linked to theprocessor, a memory 1022. Memory 1022 stores computer program code inorder to cause the user terminal 102 to perform desired actions.Processor 1021 is configured to execute computer program code stored inmemory 1022. The user terminal further comprises memory 1024 to storeadditional data such as, for example, partial RMs. The user terminal mayfurther include at least one antenna in communication with at least onetransmitter and at least one receiver to enable communication with theGNSS 101, cellular network 103, WLANs 104, positioning server 105 and/orcollection/learning server 106. The mobile terminal processor 1021 maybe configured to provide signals to and receive signals from the atleast one transmitter and the at least one receiver, respectively.

Although not shown, the user terminal 102 may also include one or moreother structure configured to share and/or obtain data. For example, theapparatus may comprise a short-range radio frequency, RF, transceiverand/or interrogator so data may be shared with and/or obtained fromelectronic devices in accordance with RF techniques. The user terminalmay comprise other short-range transceivers, such as, for example, aninfrared, IR, transceiver, a Bluetooth™, BT, transceiver operating usingBluetooth™ brand wireless technology developed by the Bluetooth™ SpecialInterest Group, a wireless universal serial bus, USB, transceiver and/orthe like. The Bluetooth™ transceiver may be capable of operatingaccording to low power or ultra-low power Bluetooth™ technology, forexample, Bluetooth low energy, radio standards. In this regard, the userterminal 102 and, in particular, the short-range transceiver may becapable of transmitting data to and/or receiving data from electronicdevices within proximity of the apparatus, such as within 10 meters, forexample. The apparatus may be capable of transmitting and/or receivingdata from electronic devices according to various wireless networkingtechniques, including 6LoWpan, Wi-Fi, Wi-Fi low power, IEEE 802.15techniques, IEEE 802.16 techniques, and/or the like.

The user terminal 102 may further comprise a collection client 1023.Collection client 1023 may comprise, for example, a software modulestored in memory 1022, or in another memory comprised in user terminal102. The collection client 1023 may be configured to collect informationcomprising at least one of the following to be sent to thecollection/learning server 106:

-   -   An estimate of the user terminal's location based on, for        example, received satellite signals of the GNSS 101    -   Measurements taken from signals of the cellular network 103.    -   Results of scanning for WLAN systems 104.    -   Results of scanning for other short range radio signals.

The collection/learning server 106 receives this information and basedon it, builds a database of AP locations and coverage areas of cellularbase stations and APs, such as for example WLAN APs. Such a database maybe called a global RM database 107 since the RMs stored in this databasemay not be specific to a country or a city, or more generally to aspecific locality. Rather, they may be global in nature. In someembodiments, collection/learning server 106 is configured to build adatabase of AP locations that does not comprise information on coverageareas of cellular base stations.

Once a reliable global RM database 107 is built, the positioning server105 may serve online positioning requests from user terminals. A userterminal may take measurements of signals from cellular networks and/orperform WLAN scans and send them to the positioning server 105. Thepositioning server may refer to the global RM database and based atleast in part upon the information provided by the user terminal,provide an estimate of the user terminal position.

If a data connection between the positioning server and a user terminalis unavailable or is undesirable, the terminal may rely on thepositioning engine 1025 to serve positioning requests offline. A partialRM or a subset of the global RM in form of RM offline files, such as forexample WLAN offline files, may be stored in the memory 1024 of the userterminal. With a partial RM pertaining to the area in which a userterminal is presently located stored in a memory of the user terminal,the user terminal may scan the WLANs and/or signals from cellularnetworks at its location and provide a list of observed AP identifiersand/or base station identities to the positioning engine 1025. Afterconsulting a partial RM stored in the user terminal 102 and based uponthe observed AP identifiers and/or the base station identities, thepositioning engine 1025 may estimate a location of the user terminalwithout sending a request to a positioning server. It should be notedthat partial RMs may be based upon access points of short range wirelesssystems other than WLAN systems and a user terminal may scan for signalsfrom at least one of these other short range wireless systems toestimate its position.

FIG. 2 shows an example system for generating and distributing partialRMs for offline usage in user terminals. In accordance with anembodiment of the present invention, an offline WLAN RM generator,OW-RMG, 201 takes as inputs a global RM from a global database 202 and alist of WLAN APs to be included in a partial RM from an AP selector forpartial RMs 203. In order to reduce a size of a partial RM, it isdesirable to include only a subset of all APs in a partial RM to bestored on a user terminal. The AP selector for partial RMs 203 helpsachieve this goal by identifying APs which are relevant to theperformance of partial RMs. The AP selector for partial RMs 203 maycomprise a memory. The selection of APs by the AP selector for partialRMs 203 may be based at least in part on the inputs provided by a userterminal 206. The OW-RMG 201 may further refine the list of APs receivedfrom the selector 203 based upon a set of at least one criterion. TheOW-RMG 201 may compress identifiers of a subset of APs in order toreduce a size of a partial RM file. The OW-RMG 201 generates partial RMsbased at least in part upon these inputs and transfers them for storageto the offline WLAN RM database 204. The partial RMs needed by the userterminal 206 are then transferred by the offline WLAN RM database 204 tothe RM offline download server 205. In an embodiment of the invention,after transferring a partial RM to the RM offline download server 205,the OW-RMG 201 may generate a newer version of the transferred partialRM. This newer version may be generated after a predetermined period oftime has lapsed after generation of the transferred partial RM, forexample. The OW-RMG 201 may compare the transferred partial RM and thenewer version and if the newer partial RM is significantly different,the OW-RMG 201 may transfer the newer partial RM to the RM offlinedownload server 205 for download by a positioning client, such as userterminal 206, for example.

In an embodiment of the invention, the offline WLAN RM database 204 maybe absent and a partial RM file may be transmitted directly from theOW-RMG 201 to the RM offline download server 205. From the downloadserver, a partial RM file may be downloaded by the user terminal 206 orany other user terminal. The user terminal may have the structure andcircuitry of user terminal 102 of FIG. 1, for example. The user terminalmay include at least one antenna in communication with at least onetransmitter and at least one receiver to enable communication with thedownload server. Similarly, the download server may include at least oneantenna in communication with at least one transmitter and at least onereceiver to enable communication with the user terminal. The downloadserver may further include a processor configured to provide signals toand receive signals from the transmitter and receiver, respectively.

Global RM database 202, AP selector for partial RMs 203, Offline WLAN RMgenerator 201, Offline WLAN RM database 204 and RM offline downloadserver 205 may be implemented as standalone nodes in a network, oralternatively at least two and optionally even all of them may beimplemented as functions in a single physical server.

FIG. 3 shows an apparatus embodying a process for updating a partial RMaccording to an example embodiment of the invention. As an example,apparatus 300 may be comprised in the OW-RMG 201 of FIG. 2. Apparatus300 comprises processors 301, 303, 304, 305, 306 and, linked to theseprocessors, a memory 307. The processors 301, 303, 304, 305, 306 may,for example, be embodied as various means including circuitry, at leastone processing core, one or more microprocessors with accompanyingdigital signal processor(s), one or more processor(s) without anaccompanying digital signal processor, one or more coprocessors, one ormore multi-core processors, one or more controllers, processingcircuitry, one or more computers, various other processing elementsincluding integrated circuits such as, for example, an applicationspecific integrated circuit, ASIC, or field programmable gate array,FPGA, or some combination thereof. A processor comprising exactly oneprocessing core may be referred to as a single-core processor, while aprocessor comprising more than one processing core may be referred to asa multi-core processor. Accordingly, although illustrated in FIG. 3 assingle processors, in some embodiments the processors 303, 304, 305, 306may comprise a plurality of processors or processing cores. Similarly,processors 303, 304, 305, 306 may be embodied within one processor 301.In some embodiments, at least one of processors 303, 304, 305 and 306are implemented at least in part in software, which software may be runon processor 301. Memory 307 stores computer program code for supportingupdating a partial RM. Processors 301, 303, 304, 305, 306 are configuredto execute computer program code stored in memory 307 in order to causethe apparatus to perform desired actions. Apparatus 300 furthercomprises memory 302. Memory 302 may be used, at least in part, to storeinput data needed for operations of the apparatus 300 or output dataresulting from operation of the apparatus 300. Apparatus 300 could becomprised in a server or any other suitable device. Apparatus 300 couldequally be a module, like a chip, circuitry on a chip or a plug-inboard, for use in a server or for any other device. Optionally,apparatus 300 could comprise various other components, such as forexample at least one of a user interface, a further memory and a furtherprocessor. Memory 302 and memory 307 may be distinct memories, oralternatively memory 307 may be comprised in memory 302, or memory 302may be comprised in memory 307.

The RM generator 303 may generate a partial RM corresponding to apre-determined geographical area, based at least in part on apredetermined criterion. The predetermined criterion may be that apredetermined time period has elapsed since a partial RM correspondingto the geographical area was generated, for example. In some embodimentsof the invention, the predetermined criterion may be that a change hasoccurred in a WLAN or cellular environment of the geographical areacorresponding to the partial RM. A change in a WLAN environment may bean increase in a number of APs, a decrease in a number of APs or achange in location of APs, for example. A change in a cellularenvironment may comprise, for example, a changed geographicalarrangement of base stations or base station identitites. The RMgenerator may transfer the generated partial RM to the comparison unit304 or it may store the generated partial RM in a memory comprised inthe apparatus 300, such as memory 302, for example.

The comparison unit 304 receives the partial RM generated by the RMgenerator 303. The comparison unit 304 may receive the partial RM fromthe RM generator 303 or it may obtain it from a memory, such as memory302, for example. The comparison unit 303 also receives a previousversion of the generated RM. A previous version of the generated partialRM may be a partial RM corresponding to the geographical area of thegenerated partial RM but which was generated prior to more than apredetermined time interval, for example. In another embodiment of theinvention, a previous version of the generated RM may be a RM thatcorresponds to the geographical area of the partial RM generated by theRM generator 303 but which was generated before a change took place in aWLAN environment of the geographical area. A change in a WLANenvironment may be an increase in a number of, a decrease in a number ofAPs or a change in location of one or more APs, for example. Thecomparison unit 304 may receive the previous version of the RM from theinterface 309 or from a memory comprised within the apparatus 300, suchas memory 302, for example.

Interface 309, which may be a data interface, may receive the previousversion of the partial RM from a database such as offline WLAN RMdatabase 204 of FIG. 2, for example. Once received by the interface 309,the previous version of the partial RM may be stored in a memorycomprised within apparatus 300, such as memory 302 or memory 307, forexample.

The comparison unit 304 compares the partial RM generated by the RMgenerator 303 and a previous version of the generated partial RM. Basedupon a comparison of the generated partial RM and the previous versionof the generated partial RM, the comparison unit 304 may determine atleast one of the following statistics:

-   -   Number of APs which are comprised in the previous version of the        generated partial RM but are not comprised in the generated        partial RM.    -   Number of APs which are not comprised in the previous version of        the generated partial RM but are comprised in the generated        partial RM.    -   Number of APs with substantially different locations in the        previous version of the generated partial RM and the generated        partial RM. Herein, two locations are said to be substantially        different if a distance between the two locations is more than a        threshold. In other words, APs have moved.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the previous version of the generated partial RM but are not        assigned to the at least one node in the generated partial RM.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the generated RM but are not assigned to the at least one        node in the previous version of the generated partial RM.

Based upon at least on of the statistics, the comparison unit 304 makesa determination of whether the generated partial RM should replace itsprevious version. The determination to replace the previous version ofthe generated partial RM by the partial RM generated by the RM generator303 may be made if at least one of the following conditions is true:

-   -   Number of APs which are comprised in the previous version of the        generated partial RM but are not comprised in the generated        partial RM exceeds a threshold value.    -   Number of APs which are not comprised in the previous version of        the generated partial RM but are comprised in the generated        partial RM exceeds a threshold value.    -   Number of APs with substantially different locations in the        previous version of the generated partial RM and the generated        partial RM exceeds a threshold value. This may correspond to a        number of APs that have moved.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the previous version of the generated partial RM but are not        assigned to the at least one node in the generated partial RM        exceeds a threshold value.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the generated RM but are not assigned to the at least one        node in the previous version of the generated partial RM exceeds        a threshold value.

The RM management unit 305 obtains the determination made by thecomparison unit 304. The determination may be transmitted from thecomparison unit 304 to the RM management unit 305 or it may be stored ina memory location by the comparison unit 304 and may be obtained fromthe memory by the RM management unit 305. In case the comparison unit304 determines not to replace the previous version of the generatedpartial RM, the RM management unit takes no further action. In case thecomparison unit determines to replace the previous version of thegenerated partial RM, the RM management unit 305 may replace theprevious version of the generated partial RM with the partial RMgenerated by the RM generator 303 in at least one database. The at leastone database may be comprised in the offline WLAN RM database 204 ofFIG. 2 or in RM offline download server 205 of FIG. 2, for example. TheRM management unit 305 may also cause a notification to be transmittedto a user terminal, such as user terminal 206 of FIG. 2, notifying thata new version of a partial RM is available.

Note that other statistics can also be utilized and the invention is notrestricted to statistics described herein.

FIG. 4 is a flow diagram showing operations for updating radio maps inaccordance with at least one embodiment of the invention. The method maybe executed by an apparatus, such as apparatus 300 of FIG. 3, forexample. In step 401, a new version of a previously generated partial RMis generated. The previously generated partial RM may be called an oldversion of the partial RM. Generation of the new version may betriggered based at least in part on a predetermined criterion. Thepredetermined criterion may be that a predetermined time period haselapsed since the old version was generated, for example. In someembodiments of the invention, the predetermined criterion may be that achange has occurred in a WLAN environment of a geographical areacorresponding to the partial RM. A change may be an increase in a numberof APs, a decrease in a number of APs or a change in location of APs,for example.

In step 402, a comparison is made between the new version of the partialRM and the old version. The comparison may involve determination of atleast one of the following statistics:

-   -   Number of APs which are comprised in the old version of the        partial RM but are not comprised in the new version partial RM.    -   Number of APs which are not comprised in the old version of the        partial RM but are comprised in the new version of the partial        RM.    -   Number of APs with a substantially different location in the old        version of the partial RM and the new version of the partial RM.        Herein, two locations are said to be substantially different if        a distance between the two locations is more than a threshold.        This may correspond to a number of APs that have moved.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the old version of the generated partial RM but are not        assigned to the at least one node in the new version of the        partial RM.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the new version of the partial RM but are not assigned to the        at least one node in the old version of the partial RM.

Based upon the statistics determined in step 402, a determination ismade in step 403 as to whether the new version of the partial RM shouldreplace the old version. The determination to replace the old version ofthe partial RM by the new version may be made if the new and the oldversions differ significantly. In an embodiment of the invention, theold and the new versions are determined to differ significantly if atleast one of the following conditions is true:

-   -   Number of APs which are comprised in the old version of the        partial RM but are not comprised in the new version of the        partial RM exceeds a threshold value.    -   Number of APs which are not comprised in the old version of the        partial RM but are comprised in the new version of the partial        RM exceeds a threshold value.    -   Number of APs with substantially different locations in the old        version of the partial RM and the new version of the partial RM        exceeds a threshold value. Herein, two locations are said to be        substantially different if a distance between the two locations        is more than a threshold.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the previous version of the generated partial RM but are not        assigned to the at least one node in the new version of the        partial RM exceeds a threshold value.    -   If the geographical area is mapped to a grid comprising nodes, a        number of access points that are assigned to at least one node        in the new version of the partial RM but are not assigned to the        at least one node in the old version of the generated partial RM        exceeds a threshold value.

If in step 403, it is determined that the old version and the newversion of the partial RM do not differ significantly, the processproceeds to step 405 and ends. However, if in step 403, it is determinedthat the old and the new versions of the partial RM differsignificantly, then the process moves to step 404. In step 404, the oldversion of the partial RM is replaced with the new version in at leastone database of a positioning system. The at least one database may becomprised in a RM database, such as the WLAN RM database 204 of FIG. 2or it may be comprised in a download server, such as RM offline downloadserver 205 of FIG. 2, for example. In some embodiments of the invention,in step 404, a notification may be sent to a user terminal, such as userterminal 206 of FIG. 2, notifying that the new version of the partial RMis available.

Note that other statistics can also be utilized and the invention is notrestricted to statistics described herein. Also, another embodiment ofthe invention, the process of FIG. 4 may be repeated for other partialRMs in the positioning system. In yet another embodiment of theinvention, significant changes between a new an old version of a partialRM may be used as an indication that at least component in thepositioning system is malfunctioning.

If desired, the different functions discussed herein may be performed ina different order and/or concurrently with each other. Furthermore, ifdesired, one or more of the above-described functions may be optional ormay be combined.

Without in any way limiting the scope, interpretation, or application ofthe claims appearing below, a technical effect of one or more of theexample embodiments disclosed herein is to reduce a number of times apartial RM needs to be downloaded by a user terminal. Another technicaleffect of one or more of the example embodiments disclosed herein is toreplace an old partial RM with its new version only if the new versionis significantly different from the old version.

Embodiments of the present invention may be implemented in software,hardware, application logic or a combination of software, hardware andapplication logic. The software, application logic and/or hardware mayreside on memory 307, the processor 301 or electronic components, forexample. In an example embodiment, the application logic, software or aninstruction set is maintained on any one of various conventionalcomputer-readable media. In the context of this document, a“computer-readable medium” may be any media or means that can contain,store, communicate, propagate or transport the instructions for use byor in connection with an instruction execution system, apparatus, ordevice, such as a computer, with one example of a computer described anddepicted in FIG. 3. A computer-readable medium may comprise acomputer-readable non-transitory storage medium that may be any media ormeans that can contain or store the instructions for use by or inconnection with an instruction execution system, apparatus, or device,such as a computer. The scope of the invention comprises computerprograms configured to cause methods according to embodiments of theinvention to be performed.

Although various aspects of the invention are set out in the independentclaims, other aspects of the invention comprise other combinations offeatures from the described embodiments and/or the dependent claims withthe features of the independent claims, and not solely the combinationsexplicitly set out in the claims.

It is also noted herein that while the above describes exampleembodiments of the invention, these descriptions should not be viewed ina limiting sense. Rather, there are several variations and modificationswhich may be made without departing from the scope of the presentinvention as defined in the appended claims.

1.-7. (canceled)
 8. A method, comprising: comparing a first partialradio map and a second partial radio map; and determining to replace thefirst partial radio map with the second partial radio map based at leastin part on a result of the comparison.
 9. The method of claim 8, whereinthe comparing comprises: determining a first number of access pointsthat are included in the first partial radio map but not included in thesecond partial radio map; wherein the first partial radio map isdetermined to be replaced with the second partial radio map if the firstnumber of access points exceeds a threshold.
 10. The method of claim 8,wherein the comparing comprises: determining a second number of accesspoints that are not included in the first partial radio map but areincluded in the second partial radio map; wherein the first partialradio map is determined to be replaced with the second partial radio mapif the second number of access points exceeds a threshold.
 11. Themethod of claim 8, wherein the comparing comprises: determining a numberof access points with different locations in the first partial radio mapand the second partial radio map; wherein the first partial radio map isdetermined to be replaced with the second partial radio map if a numberof access points with different locations in the first partial radio mapand the second partial radio map exceeds a threshold.
 12. The method ofclaim 8, further comprising: receiving a mapping of access points in thefirst partial radio map and access points in the second partial radiomap to at least one node in a grid; wherein the comparing comprises:determining a third number of access points that are assigned to the atleast one node in the first partial radio map but are not assigned tothe at least one node in the second partial radio map; and wherein thefirst partial radio map is determined to be replaced with the secondpartial radio map if the third number of access points exceeds athreshold.
 13. The method of claim 8, further comprising receiving amapping of access points in the first partial radio map and accesspoints in the second partial radio map to at least one node in a grid;wherein the comparing comprises: determining a fourth number of accesspoints that are assigned to the at least one node in the second partialradio map but are not assigned to the at least one node in the firstpartial radio map; and wherein the first partial radio map is determinedto be replaced with the second partial radio map if the fourth number ofaccess points exceeds a threshold.
 14. The method of claim 8, whereinthe first partial radio map and the second partial radio map compriseradio maps of a same geographical area corresponding to different timeperiods.
 15. An apparatus, comprising: at least one processor; and atleast one memory including computer program code the at least one memoryand the computer program code configured to, with the at least oneprocessor, cause the apparatus to perform at least the following:comparing a first partial radio map and a second partial radio map; anddetermining to replace the first partial radio map with the secondpartial radio map based at least in part on a result of the comparison.16-20. (canceled)
 21. The apparatus of claim 15, wherein the comparingcomprises: determining a first number of access points that are includedin the first partial radio map but not included in the second partialradio map; and wherein the at least one processor is further configuredto cause the first partial radio map to be replaced with the secondpartial radio map if the first number of access points exceeds athreshold.
 22. The apparatus of claim 15, wherein the comparingcomprises: determining a second number of access points that are notincluded in the first partial radio map but are included in the secondpartial radio map; and wherein the at least one processor is furtherconfigured to cause the first partial radio map to be replaced with thesecond partial radio map if the second number of access points exceeds athreshold.
 23. The apparatus of claim 15, wherein the comparingcomprises: determining a number of access points with differentlocations in the first partial radio map and the second partial radiomap; and wherein the at least one processor is further configured tocause the first partial radio map to be replaced with the second partialradio map if the number of access points with different locations in thefirst partial radio map and the second partial radio map exceeds athreshold.
 24. The apparatus of claim 15, further comprising: a firstreceiver configured to receive a first partial radio map and a secondpartial radio map.
 25. The apparatus of claim 24, further comprising: asecond receiver configured to receive a mapping of access points in thefirst partial radio map and access points in the second partial radiomap to at least one node in a grid; wherein the comparing comprises:determining a third number of access points that are assigned to the atleast one node in the first partial radio map but are not assigned tothe at least one node in the second partial radio map; and wherein theat least one processor is further configured to determine to cause thefirst partial radio map to be replaced with the second partial radio mapif the third number of access points exceeds a threshold.
 26. Theapparatus of claim 24, further comprising: a second receiver configuredto receive a mapping of access points in the first partial radio map andaccess points in the second partial radio map to at least one node in agrid; wherein the comparing comprises: determining a fourth number ofaccess points that are assigned to the at least one node in the secondpartial radio map but are not assigned to the at least one node in thefirst partial radio map; and wherein the at least one processor isfurther configured to cause the first partial radio map to be replacedwith the second partial radio map if the fourth number of access pointsexceeds a threshold.
 27. The apparatus claim 15, wherein the firstpartial radio map and the second partial radio map comprise radio mapsof a same geographical area corresponding to different time periods.